The exhausted Ferrer, playing in his seventh straight week of tournament play, battled valiantly for a set and a half, even fighting back from 5-2 down to take the opening set.
But ultimately Wawrinka had too much for the world number three, and secured the win after just less than two and a half hours.
It is almost certain to bring Wawrinka the reward of a place in the last four: only an improbable victory by Tomas Berdych over Rafael Nadal in the final Group A tie on Friday night would deny the Swiss number two a spot in the semi-finals.
Nadal is already sure of his place in the last four, but Berdych needs to end his miserable run of 15 consecutive defeats at the hands of the Spaniard.
If Berdych loses to Nadal, Wawrinka will go through to the semi-finals as runner-up behind the world number one.